1. Field of the Invention
The invention relates generally to moisture resistant compositions and in particular to moisture resistant compositions comprising a polyimide copolymer.
2. Background
There is a continuing need for polymers having good manufacturing and performance properties at elevated temperatures. Certain manufacturing properties at elevated temperatures are particularly needed, for example: metalizability, dimensional stability, and resistance to warpage. Likewise, certain performance properties are particularly needed, for example: moisture resistance.
Lighting reflectors, especially for automotive applications, require materials that can withstand the high heat produced by light sources, that have excellent dimensional stability to focus the light in a tight pattern at long distances, and that can be easily processed into complex shapes. These reflectors are usually coated with a metal, such as aluminum, to provide a highly reflective surface. To achieve this high degree of reflectivity with low haze, a very smooth pre-coated surface is required. In order to achieve consistently such a smooth pre-coated surface, it has typically been necessary to base coat the molded reflector with a primer prior to coating the reflector with metal. Direct metalization of molded parts is also challenging because it introduces the additional requirements of good adhesion of the metal to the molded part and a very smooth surface of the part as molded.
In electronic components there has been a move to leadless solder at least partially because of the deleterious effects caused by lead on the environment. Replacement solders have higher melting points than lead based solders and so polymers capable of withstanding the additional heat necessary to melt the lead replacement solders are needed for use as, for example, substrates or coatings in close proximity to soldering points. Even uses such as polymer parts feeling the heat from jet engine wash, lead a continuing demand for polymers having higher heat properties than those currently on the market.
Several classes of high heat polymers are known in the art. Polyetherimide resins are known for high heat distortion temperatures and high glass transition temperatures that make their use as coatings, molded articles, composites, and the like very attractive where high temperature resistance is desired. Due to their high glass transition temperature and high melt viscosity, however, polyetherimides can be difficult to process into finished products. Additionally, improvements are needed in the moisture resistance and metalizability of compositions comprising polyetherimide resins for leadless solderable articles.
For the foregoing reasons, there is a need for metalizable, moisture resistant compositions useful for lead free solderable articles. There is also a need for a method of producing a metalized coating without a primer.